using System;

using Org.BouncyCastle.Math;
using Org.BouncyCastle.Math.EC;

namespace Org.BouncyCastle.Asn1.X9
{
    /**
     * Class for processing an ECFieldElement as a DER object.
     */
    public class X9FieldElement
        : Asn1Encodable
    {
		private ECFieldElement f;

		public X9FieldElement(
			ECFieldElement f)
		{
			this.f = f;
		}

		public X9FieldElement(
			BigInteger		p,
			Asn1OctetString	s)
			: this(new FpFieldElement(p, new BigInteger(1, s.GetOctets())))
		{
		}

		public X9FieldElement(
			int				m,
			int				k1,
			int				k2,
			int				k3,
			Asn1OctetString	s)
			: this(new F2mFieldElement(m, k1, k2, k3, new BigInteger(1, s.GetOctets())))
		{
		}

		public ECFieldElement Value
        {
            get { return f; }
        }

		/**
		 * Produce an object suitable for an Asn1OutputStream.
		 * <pre>
		 *  FieldElement ::= OCTET STRING
		 * </pre>
		 * <p>
		 * <ol>
		 * <li> if <i>q</i> is an odd prime then the field element is
		 * processed as an Integer and converted to an octet string
		 * according to x 9.62 4.3.1.</li>
		 * <li> if <i>q</i> is 2<sup>m</sup> then the bit string
		 * contained in the field element is converted into an octet
		 * string with the same ordering padded at the front if necessary.
		 * </li>
		 * </ol>
		 * </p>
		 */
		public override Asn1Object ToAsn1Object()
		{
			int byteCount = X9IntegerConverter.GetByteLength(f);
			byte[] paddedBigInteger = X9IntegerConverter.IntegerToBytes(f.ToBigInteger(), byteCount);

			return new DerOctetString(paddedBigInteger);
		}
    }
}
